With a development of telecommunication industry and an establishment of an information society, modern consumers demand electronic devices which have a number of functions and excellent data processing capabilities which are easily available at any place. Electronic device manufacturers are competitively releasing the electronic devices which are compact and have the excellent data processing capabilities to meet the needs of these consumers.
For example, in an electronic device which is commonly referred to as “a smart phone,” all auxiliary devices such as a GPS receiver, a camera, and a local area network connecting device as well as a basic function of a mobile phone are being integrated by applying a high-performance data processor, a memory, a high-resolution display, and an image processing chip. Further, the smart phone may provide various functions such as full Internet connectivity, entertainment including a full-resolution video, a navigator, Internet banking, and the like in a pocket-sized device. Therefore, in a portable electronic device such as the smart phone, demands for packaging a number of electronic circuit devices in a small space and physically disposing the electronic circuit devices in more compact arrangement, are becoming more and more intense along with a rapid development of the portable electronic devices.
In the miniaturized electronic device, a number of circuits should be integrated in a small space, and thus there is a disadvantage that these are easily subject to influence from an electric wave noise. Further, an EMI is generated in the electronic device due to an electromagnetic wave that is generated from the electronic device itself, or that ingresses the electronic device from the outside, or that flows through a connected circuit line. In order to reduce harmful effects caused by the electromagnetic wave, conventionally, a method of installing an EMI shielding structure of a conductive material to block the electromagnetic wave and covering a predetermined region of the electronic circuit board, has been used.
Meanwhile, the electronic device inevitably generates heat due to a characteristic of a material itself and an electrical resistance occurring on a connection part of respective components during the operation of the device. As the generated heat increases a temperature of the operating component, the generated heat is the cause of reduced service life of the electronic device, and specifically, it tends to cause a malfunction to occur above a specific temperature, or to make it difficult for the influenced component to demonstrate maximum performance. In addition, considering that a miniaturization and an integration of the electronic device lead to an increasing number of circuits included in a unit area and to more serious heat generation issue, the heat generation of the miniaturized electronic device has emerged as a serious concern. An active cooling method of using a cooling fan as a method of cooling shows the highest cooling performance, but with problem such as noise generated from the cooling fan and power consumption necessary for the operation of a cooling device. Additionally, since additional electronic circuits and component spaces are required, there is a disadvantage that a miniaturization of the product, which is a recent trend of the electronic device, is becoming difficult. Therefore, a passive cooling method which emits the heat to the outside using a thermal pad, etc. is mainly used. Since the passive cooling method causes heat to dissipate to outside simply through the thermal pad, etc., power is not necessarily required for operating the device, noise does not occur, and a greater degree of freedom can be granted in terms of the design of the electronic device, compared to the method of using the cooling fan.
It is important that the thermal pad which uses heat transfer by conduction is in close contact with the electronic circuit. However, when a space is generated between the electronic circuit and the thermal pad, the heat transfer efficiency deteriorates in the space, and temperature is partially increased, thus leading into both malfunctions of the electronic circuit and a reduction in durability. Therefore, it is necessary that the thermal pad uses a material capable of ensuring adhesion with the electronic device.
Further, since the malfunctions and reduced durability of the device, and a risk of accident as well as a waste of the power can be caused when a leakage current occurs on a thermal plate or an outer surface of a product, which is made of metal material, the thermal pad should have a high electrical insulation characteristic in addition to an excellent cooling effect. Therefore, a development of a new thermal pad, with improved thermal conductivity and the electrical insulation characteristic than the conventional thermal pad, and specifically, applicability to a miniaturized electronic device, is necessary.